The immensity of the nuclear scaleup effort (and the associated electrification of everything) that will be required to achieve the 430-530 ppm scenarios is almost beyond imagination. Given that nuclear is the only energy source to have actually declined over the course of the 21st century (while coal use exploded), I would not get my hopes up.
That being said, I'm all for nuclear and really hope that new designs live up to expectations, but it remains a capital intensive technology which is limited to new infrastrucutre for electricity production with a long history of strong societal resistance and cost escalations. For these reasons, none of the mainstream rapid decarbonization pathways (e.g. IEA & IPCC) consider a leading role for nuclear. For example, the IEA Energy Technology Perspectives 2014 report gives the breakdown of CO2 avoidance towards the 2 deg C scenario as follows:
Fuel switching: 10%
Power generation efficiency: 2%
However, this is under the highly unlikely scenario of an idealized globally coordinated CO2 mitigation effort starting immediately and it only extends up to 2050. If climate science is correct and the world is eventually forced to commit to the 2 deg C scenario, the emissions pathway will be one of retroactive emissions cuts and large overhoot - a pathway where the unique attributes of CCS really come to the fore as described in my previous articles here and here.
These longer-term pathways are perhaps best illustrated in the latest IPCC report. Take a look at Figure 7.10 here for a clear graphical representation of three different projected energy technology portfolios.
About the discount rate, I will be very surprised if nuclear ever gets the preferential treatment of solar PV. Solar is ideologically extremely attractive to the general public while nuclear is still viewed negatively. I don't like this any more than you do, but it is the reality we have to deal with. The chances that preferential treatment of nuclear (similar to PV) takes off any time soon therefore appear to be extremely low.
In theory, since electricity capacity in China is expanding at a rate of about 10% p.a., new power infrastructure should be discounted at a 10% rate + a substantial risk premium. Underpricing of financial capital will lead to the uneconomical deployment of technologies that require high up-front investments of materials, energy and expertise, thereby slowing down deployment and hurting economic growth (and the ability to make ever increasing investments in future energy infrastructure).